316 PROCEEDINGS OF THE AMERICAN ACADEMY 



of this acid with monobrommaleic and monobromfumaric acid, and its 

 strongly naarked dibasic cliaracter, made its constitution a question of 

 decided interest. We therefore undertook its more extended inves- 

 tigation, as well as a study of the analogous chlorine compound, which 

 could readily be obtained from mucochloric acid. Although our in- 

 vestigations are in many respects incomplete, they seem to us to leave 

 little doubt as to the constitution of the compounds in question ; and 

 since we shall be unable to continue the work together, we have thouiiht 

 it best to present the results which we have already obtained. 



Mucoxybromic Acid. 



Whenever mucobromic acid is dissolved in a solution of an alkaline 

 hydrate, more or less mucoxybromic acid appears to be formed. For 

 its preparation, however, we have found it necessary to use baric 

 hydrate, and the yield is then largely dependent upon the conditions 

 under which the I'eaction takes place. We have found it most advan- 

 tageous to suspend the mucobromic acid in thirty parts of cold water, 

 and, after cooling well with ice, to add gradually, with constant shak- 

 ing, finely powdered baric hydrate of known strength. After the 

 mucobromic acid is neutralized, the baric hydrate must be added in 

 small quantities, and the solution allowed to stand until the alkaline 

 reaction has nearly disappeared before a fresh portion is added. The 

 alkaline reaction disappears rapidly at first, afterwards more slowly, 

 and when the amount of baric hydrate demanded by the equation 



2 C^H^Br^O. + 3 BaO^H, = 2 BaCJlBrO, -f BaBr^ + 4 II^O 



has been added, the reaction usually remains feebly alkaline, even 

 after long standing. The slight excess of baric hydrate is then re- 

 moved by carbonic dioxide, and an equal volume of alcohol added to 

 the filtered solution. Baric mucoxybromate, which is very sparingly 

 soluble in dilute alcohol, is thus precipitated in the form of fine, flat- 

 tened, pointed needles, and may be purified by dissolving in cold water 

 and reprecipitating with alcohol. With careful work, about sixty per 

 cent of the theoretical yield may be obtained. The preparation of the 

 free acid from the barium salt is a matter of considerable difficulty, 

 since it cannot be extracted from aqueous solution by the ordinary 

 solvents, and it is quickly decomposed during the evaporation of its 

 solution, even at ordinary temperatures. We succeeded in preparing 

 it only by moistening the salt with a little water, precipitating the 

 barium exactly with sulphuric acid, and evaporating the concentrated 

 solution of the acid thus obtained as rapidly as possible over sulphuric 



